1. Field of the Invention.
The present invention relates to a method and an apparatus for developing a test strip, and more particularly a test strip having a reagent test pad requiring an incubation period for developing the desired test results disposed thereon.
2. Description of the Related Art.
Test strips having a reagent test pad disposed thereon are conventionally known testing devices which are often used to determine whether a sufficient concentration of a chemical or chemicals is present in a solution. In the conventionally known procedure, the reagent test pad having reagent chemicals disposed thereon is placed in contact with a solution to be tested, typically by dipping the test strip in the solution. When the reagent test pad is sufficiently wetted, the test pad is removed from the solution and the indication on the test pad is examined after a predetermined waiting time. The reagent test pad is usually designed to change to a particular color or range of colors corresponding to the concentration of the chemicals in the solution being examined. In conventionally known procedures, the user places the wetted test pad in an open environment, such as on a lab bench, while waiting for the color change to develop.
Although simple to use, one consideration in using such test strips is the accuracy and reliability of the color indications developed on the reagent test pads. In conventional applications, a standardized chart showing various colors and corresponding concentrations is provided. To be effective and reliable, the test performed should always produce a color which corresponds to an accurate concentration of the chemical being tested. In other words, the person performing the test should be able to confidently match the color produced by the test strip with a corresponding color on the standardized chart and the concentration of chemical then taken therefrom.
Unfortunately, due to the imprecision inherent in any analytical tests, the desired indication may be observed at concentrations other than the predetermined concentration. For example, in a test producing a mere change in color at a given concentration, such color change could incorrectly occur at a concentration other than the given concentration. The concentration at which the test always reads "PASS" or "FAIL" is determined by the properties and conditions of the test. The difference in the 100% FAIL and the 100% PASS concentration may be called the "window". It is desirable to have the range of this window be as small as possible to ensure effective management and use of the solutions being tested, for example to ensure that only effective solutions are used and to ensure that effective solutions are not needlessly replaced.
The window may be narrowed in many tests by increasing the reaction time between the chemicals in the reagent test pad and the chemicals in the solution. This is most likely due to two factors associated with dry reagents tests, namely 1) the reactants on the test strip need time to completely dissolve, and 2) the diffusion of reactants in a solid matrix is very slow. However, because these reactions occur in aqueous solutions, the reaction time available for the test is limited by the evaporation of water from the reagent test pad. Accurate measurement within a narrow window is difficult if the moisture necessary to maintain the reagents in solution evaporates from the reagent test pad before the reaction is complete. This is particularly true when measuring highly concentrated analytes where the loss of even small amounts of water may cause precipitation of analytes and/or reactants within the test pad.
Conventionally known methods and apparatuses are limited in their ability to obtain accurate and reliable results within a narrow window because the water necessary to maintain the reagents in solution typically evaporates from the test pad before allowing a sufficient incubation period. This evaporation leads to improper use of ineffective solutions as well as wasteful replacement of effective solutions.
Therefore, what is needed is an accurate and reliable method and apparatus for using test strips described above wherein a sufficient incubation period is provided to allow the reagents to completely react with one another before the requisite moisture evaporates from the test pad.